1. Field of the Invention
The invention relates to an assembly of a micro-plate and a lid that can be manipulated by robotic stackers and/or by robotic arms.
2. Description of the Related Art
Many laboratory procedures require analysis to be performed on chemicals or biological specimens, such as tissue cultured cells, proteins and enzymes. The specimen may be deposited in a liquid growth medium or buffer. An analysis then is performed after a specified time which will vary depending upon the nature of the biological specimen and the type of analysis that is to be performed.
The chemical or biological specimen often is deposited in a micro-plate. The plate may be moved from a first location where the specimen is deposited to a second location where the specimen is permitted to grow or otherwise develop over a specified time. The specimen then will be moved to another location for analysis.
The typical micro-plate for performing the above-described laboratory analysis is rectangular with a bottom wall, upstanding sidewalls and an open top. A lid may be mounted to the open top of the sidewalls to control evaporation. The footprint defined by the bottom wall of the plate generally is one of several standard sizes dimensioned to accommodate robotic handling equipment in a laboratory. Other characteristics of the plates, however, vary considerably from one manufacturer to another and from one type of analysis to another. One significant difference relates to the number of biological specimens that can be accommodated in the plate. For example, some plates define a single large reservoir in which tissue cultures may grow. Other laboratory analysis can be carried out with low volume assays. Thus, a single plate can accommodate a plurality of wells into which liquid and/or tissue cultures can be deposited. The plurality of wells typically are arranged in a rectangular matrix with formats that conform to standard formats for pipettes. For example, some standardized micro-plates include 2, 4, 8, 24, 96, 384, 1,536, 3456, or 4,080 wells.
A micro-plate with an appropriate number of wells can be molded unitarily in a dedicated mold for the particular number of wells. However, some micro-plates are formed from plural parts that are assembled together. For example, the micro-plate may include a unitary frame and a separate unitary well array with a pattern of wells. The well array with an appropriate number of wells is assembled to the standard frame.
Micro-plates often are stored in stacked arrays in the laboratory while the tissue or other biological material in the wells is permitted to grow. The micro-plates then are moved from the stacked array robotically and are transferred to appropriate work stations for analysis. There are two different approaches for robotically transferring the micro-plates from the stacked array to the work station for analysis. One option employs robotic gripping devices with grippers or fingers that grab opposite sides of the plates for transfer to a work station. Robotic grippers generally function to grab the top plate in a stacked array. The robotic grippers then lift the plate from the top of the stack and transfer the plate to the appropriate work station. Other laboratory devices stack the micro-plates in a magazine that permits the plates to be removed sequentially from the bottom of the stacked array. More particularly, the stack of plates may rest on two sets of solenoid controlled pins or levers that can retract and extend. Retraction of the pins releases the bottom plate in the array. The pins then extend to catch beneath the next plate, while the remaining stack of plates indexes down one position. The bottom plate is released onto an elevator lift that rises up from a location beneath the stacked array to engage the plate and to keep the plate aligned horizontally, thereby avoiding spills. The plate then is lowered by the elevator lift onto a shuttle that moves the plate to the appropriate work station.
Robotic grippers must have specialized features for contacting the plate. These features may include gripper pads, gripper points, gripper fingers or a serrated edge. These gripping features typically require smooth uninterrupted flat surfaces on the plate and/or the lid for proper engagement. Many plates can be handled efficiently by robotic grippers when the plate is stored independently of a lid. However, robotic grippers are likely to encounter gripping difficulties when the plate is being manipulated with the lid in place. More particularly, the known plate/lid assemblies are not configured for simultaneously gripping the lid and the plate in a manner that will hold the plate and lid in their assembled condition. There is the potential that the robotic gripper will grip only the lid or that the robotic gripper will grip portions of the lid below the top-most plate in a stacked array. Thus, many plates are stacked without lids to facilitate manipulation by robotic grippers. However, the absence of a lid significantly increases evaporation rates.
Robotic stackers that remove plates sequentially from a stacked array also encounter problems with lids. More specifically, the stacker is not well suited to distinguishing between a plate and a lid. Thus, the stacker may drop just the plate from the magazine, while retaining the lid for the dropped plate. The next cycle, then will drop the retained lid.
In view of the above, it is an object of the subject invention to provide a plate and lid assembly that is well suited to robotic handling by both robotic grippers and stackers.
It is another object of the subject invention to provide a micro-plate molding method for efficiently producing plates with a plurality of different well arrays.
A further object of the subject invention is to provide a plate and lid assembly that resists evaporation and facilitates robotic manipulation.